1. Field of the Invention
The present invention relates to key pad devices having some form of illumination for reading the key pad in darkened environments, and more particularly to a key pad having components which exhibit phosphorescence.
2. Description of the Prior Art
Key pads, particularly those used for controlling electronic devices, have come into very wide spread use. Frequently these key pads are used in environments that are dimily lit, or even not lit at all. In such circumstances, the user must use his/her memory to press the appropriate function key. If the use relates to a television or vidocassette recorder and an error pressing keys is made, there is little difficulty beyond perhaps some annoyance. However, if the key pad controls a device that is either dangerous (as for example in an industrial setting) or critical to human life (as for example in a hospital setting) then an accidental mistake at key pressing can result in a calamity. Clearly what is needed is an illumination system for key pads.
In the prior art there are numerous attempts at providing an illumination system for a key pad. One class of such devices is a self-contained illumination system having a battery and light which clips onto the key pad of a remote control. Examples of this first class of devices are U.S. Pat. Nos. 4,949,230 to Burmeister, dated Aug. 14, 1990; 4,905,127 to Kaminski, dated Feb. 27, 1990; and 4,893,222 to Mintzer, dated Jan. 9, 1990. A second class of such devices utilizes a key pad having lighted keys. An example of this second class of devices in U.S. Pat. No. 4,449,024 to Stracener, dated May 15, 1984. A third class of such devices utilizes an optical conductor to transmit illumination from a light source to the keys of the key pad. Examples of this third class of devices are U.S. Pat. Nos. 4,343,975 to Sado, dated Aug. 10, 1982 and 4,247,747 Swatten, dated Jan. 27, 1981.
In each of the prior art illumination devices, some form of illumination source is utilized which requires a power supply, internal or external, to operate. This requirement necessitates bulky and heavy structural configurations and multiple problems associated with electrical power provisions. What is needed is an illumination system for a key pad which requires no power supply connected thereto to operate it.